John Leonard, head of the American Swimming Coaches Association and a leading light at the global equivalent, WSCA, today described Ye Shiwen's last 100m, 58.68sec, of the 400m medley on her way to a 4:28.43 world record last weekend, as "unbelievable".

"It's disturbing. I watched the six-beat kick off the wall into freestyle and thought 'here we go'. It reminded me of watching Kristin Otto (GDR) back in Madrid 1986 at the world championships leave other women behind like she was a man," said Leonard.

"It does, I'm afraid, bring back a lot of awful memories of those times," he said when asked if the sport was back in the 1990s, when China was the scourge of world swimming with more than 40 positive steroid tests and Ireland's Michelle Smith's triple gold of Atlanta was questioned 18 months before she manipulated a drug-test sample and was suspended from the sport in disgrace. She was not banned for a positive test but androstenedione was present in her urine, her own lawyer highlighted at a Court of Arbitration appeal that she lost.

Leonard, the first senior figure in the sport, to openly question the Chinese here at these Games, added: "We have to be careful what the accusation is. We simply don't know. But I would say this: the history of our sport tells us that every time we see something 'unbelievable', it more often than not turned out to be some form of cheating that was involved, doping in most cases.

"The GDR, China in the 1990s … all had excuses and explanations. It turned out they were lying. We've seen superwoman in the pool before, as supermadchens and as Chinese cheats. They were banned."

Abused by people who doped them too, the rogues in the shadows most often never questioned, let alone caught. Folk like Zhao Ming, banned for life in 1998 but back on the deck in China with children after a suspension announced in Perth 1998, the archive of cuts confirms, was apparently reduced to eight years sometime afterwards.

The trouble with Ye's swim was not the overall speed but the last 100m split, said Leonard. "It doesn't add up. She swam three competitive splits in pine wire what women are doing right now and then she unleashed an historic anomaly. There's something not quite right there."

Alongside the disgraced Ming, coaches Hiuqin Xu and Zhi Cheng also received suspensions in 1998. Hounds were set racing in London when it was reported that a coach suspended with Zhao as his assistant in the 1990s was accredited as an official at London 2012 and had been sat in the stands watching Ye's super-speed race on Sunday.

Australia's Stephanie Rice, the defeated Olympic champion from Beijing left in the wash 6sec behind Ye in London called the Chinese competitor's homecoming split "insanely fast", while the American world record holder in the 200m medley that Ye raced tonight for a place in the final, Ariana Kukors, described it as "amazing" and "unbelievable".

Asked about the accusation of doping, Ye replied: "The Chinese team keep very firmly to the anti-doping policies, so there is absolutely no problem."

Leonard said that China had "to answer a whole bunch of other questions … I spoke to coaches around the venue and no one can remember seeing anything like this. No woman has ever split the men, let alone the two greatest all-rounders in the history of the sport."

Leonard placed his faith in the new FINA Biological Passports scheme to which Ye must submit. "Blood is taken, and it can be tested for up to eight years. If there is something unusual going on in terms of genetic manipulation or something else, I Think we're going to hear about it one day, perhaps within those eight years."